Suggest Treatment For Heavy Vaginal Bleeding

Hi, I started to bleed on day 13 of my cycle, and it has not stopped. I think you could say it has clots or something with it & it is not constant through the day. It is now day 18 and I had some blood too today (not as much). I was on the pill but I get IBS and I'm now worried am I pregnant but the bleeding has been heavy to be described as spotting, definitely not spotting.